1. Field of the Invention
This invention relates, in general, to printers, copiers, duplicators and like devices which provide hard copy outputs and, more specifically, to such apparatus which uses intermediate transfer devices.
2. Description of the Prior Art
Printers, copiers, duplicators, and like devices which use a photosensitive member to develop and transfer an image ultimately to a hard copy output, such as a sheet of paper or transparency, operate and are constructed in several different modes or variations. An intermediate transfer step is used in some apparatus to transfer the images from the photosensitive member to the paper. In this type of apparatus, the image is first transferred to an intermediate roller, drum, or belt, and then transferred from that member to the paper. When color images are being produced by the intermediate process, the traditional method is to register all of the individual color component images on the intermediate transfer device to form the composite or final color image before transfer to the paper. While there are certain advantages to intermediate transfer methods, the components required can affect the size and weight of the machine.
It is usually desirable to keep the size of the intermediate transfer device as small as possible in most applications. However, in other applications, it may be desirable to make the intermediate transfer device larger than usual to allow for other mechanical parts and functions, such as space to install parts on the device or to increase the radius of curvature of the device to make the image more flat. In other cases, it may be desirable to increase the size of a transfer device to allow for placement of other necessary components, such as multiple toner stations in a color copier, in relation to other components or devices in the copier. Whether it be to increase or decrease the size of the intermediate transfer device, it is desirable, and an object of this invention, to provide an apparatus and method whereby the size of the intermediate transfer device may be changed from traditional concepts for improved machine performance and size.
It is conventional practice to make the device which is used to transfer images from the photosensitive member or belt the same effective length as the photosenstive belt, or some whole number fraction of the length of the belt, such as 1/1, 1/2, 1/3, 1/4, or 1/N, where N is any integral number. Usually this device is a roller drum, or belt which has the dimensional restrictions as stated above so that the two devices can be moved at the same speed and the images written thereto are always at the same position on the transfer member. This has been necessary in the past mostly because of mechanical discontinuities in the transfer member which required that the images be placed at a definite position on the transfer device. The practice of sizing the transfer member in an intermediate transfer process to be an integral fraction of the image belt has been carried over from the direct transfer techniques. Since the intermediate transfer member or drum can be continuous without permanently positioned mechanical paper grippers or restricted image areas, the coordination between the movements of the photosensitive belt and the intermediate transfer drum can be modified. This modification to the traditional practice is used in the present invention to permit the sizing changes in the intermediate transfer member to achieve better machine operation and size optimization.
Therefore, it is desirable, and an object of this invention, to provide an apparatus and method which permits the change in size of the intermediate transfer member without affecting the quality of the image transferred to the intermediate member.